Show the List of Installed Packages on Debian or Ubuntu

The command we need to use is dpkg –get-selections, which will give us a list of all the currently installed packages.

$ dpkg --get-selections
adduser                                         install
alsa-base                                       install
alsa-utils                                      install
apache2                                         install
apache2-mpm-prefork                             install
apache2-utils                                   install
apache2.2-common                                install
apt                                             install
apt-utils                                       install

The full list can be long and unwieldy, so it’s much easier to filter through grep to get results for the exact package you need. For instance, I wanted to see which php packages I had already installed through apt-get:

dpkg --get-selections | grep php

libapache2-mod-php5                             install
php-db                                          install
php-pear                                        install
php-sqlite3                                     install
php5                                            install
php5-cli                                        install
php5-common                                     install
php5-gd                                         install
php5-memcache                                   install
php5-mysql                                      install
php5-sqlite                                     install
php5-sqlite3                                    install
php5-xsl                                        install

For extra credit, you can find the locations of the files within a package from the list by using the dpkg -L command, such as:

dpkg -L php5-gd
/.
/usr
/usr/lib
/usr/lib/php5
/usr/lib/php5/20060613
/usr/lib/php5/20060613/gd.so
/usr/share
/usr/share/doc
/etc
/etc/php5
/etc/php5/conf.d
/etc/php5/conf.d/gd.ini
/usr/share/doc/php5-gd

Now I can take a look at the gd.ini file and change some settings around…